Telephone relay system



Jan. 14, 1941. c, RE VES 2,228,673

TELEPHONE RELAY SYSTEM Filed June 29, 1939 I6 v TELEPHONE j; LINE .77 A

Jae-3011155215 qr IMRM INVENTOR E E REEVES.

ATTORNEY Patented Jan. 14, 1941 UNITED STATES PATENT OFFICE 4 Claims.

(Granted under the act a March 3, 1883, as amended April so, 1928; 370 0. G. 157) The invention described herein may be manufactured and used by or for the Government of the United States for governmental purposes without the payment to me of any royalty thereon in accordance with the provisions of the act of April 30, 1928 (Ch. 460, Stat. L. 467) This invention relates to a relay system and more particularly to amethod of and means for automatically starting and stopping such equipment as recorders, signal lamps, alarms or time recorders responsive to the use and non-use respectively of a communication channel. A speciflc object of the invention is to provide a relay system for use in connection with a telephone subscriber's line of either the automatic or manual type for energizing a sound recording device connected to the subscriber's line responsive to the use of that line and for de-energizing the recording device responsive to the non-use of 0 that line in such a manner as to cause no impairment to the normal operation of the telephone line.

A further object of this invention is to provide audi le and/or visual signals to indicate the use 5 or non-use of a telephone line.

Other and further objects oi. the invention will be apparent from the .iollowing specification when read in connection with the accompanying drawing in which the system is shown diagrammatically.

In the drawing wires l and 2 are the wires leading from a subscribers telephone substation ii to the central oflice. Telephone wire i normally has applied thereto a negative potential while 5 telephone wire 2 has applied thereto a positive potential. Wire I is connected by way of a resistance 3 to the grid or control electrode of a trlode 4. Wire 2 is connected by means of a resistance 5 "and a source 0! biasing potential 5 with poten tiometer winding I there'across to the cathode of the tube 4. The cathode of the tube 4 is energized by the battery 8 or other appropriate source or cathcde'potential. The plate or anode of the tube 4 is connected to one terminal of the wind- 5 ing II of an electromagnetic relay. the other end or terminal of which is connected to the positive side of a source of anode potential 9 the negative side of which is connected to the cathode of the tube 4. The electromagnetic relay winding ll has associated therewith an armature H which engages with the contact i2 when the relay inding Ills energized. The armature H and contact I! are connected to a recording device, alarm or signal I! for energizing the recording device,

alarm or signal when the relay is energized. Conductors l4 and ii are connected from wires l and 2 of the telephone line respectively to the recording device l3.

The operation of the system disclosed above is substantially the same when used with an auto- 5 matic telephone line as with a manual line, but due to certain differences that will be dealt with later, the resistances 3 and 5 have been shown as variable and a'potentiometer device has been shown at l for applying a biasing potential to the grid or control electrode of the tube 4 in opposition to that applied by the telephone line. It is to be understood, however, that these devices need not be made variable but may be made to suit the particular case.

In the case of an automatic telephone system, the voltage across the line leading to a subscriber's telephone station is approximately 50 volts when the line is idle. This voltage immediately drops to about 10 volts when the receiver is raised and remains at that value during conversation until the receiver is replaced. On a manual line the voltage is usually 24-volts when idle, and approximately 7 when the receiver is raised. This voltage diil'erence is utilized to control the energization and de-energization 0!. outside equipment such as the recording device It in the following manner.v During such time as the telephone line |-2 has applied thereto the normal idle line voltage the grid or control electrode oi the tube 4 is biased to such a point that no plate current flows in the plate circuit of the tube and consequently the winding lb of the electromagnetic relay is not energized. when the receiver is lifted at the subscriber's substation It and the voltage between wires l and 2 of the line drops, the reduced line voltage is insuflicient to maintain the. grid of the tube 4 sufliciently negative to prevent plate current flow. The reduced line voltage caused by lifting the receiver permits the plate current to flow energizing the winding ll of the electromagnetic relay, the armature II is attracted to contact I! closing the circuit for the recording device i3 connected to the telephone line l-2. During such time as the telephone substation I6 is in use the recorder ll continues to iunction to record the conversation on the line. Upon replacement of the receiver at the subscriber's substation IS the normal voltage of the line again charges the grid or control electrode of the vacuum tube 4 sumciently negative as to stop plate current and release the armature I I. opening the circuit H and i2, stopping the operation of the sound recorder l3 or other alarm or signal device.

Inan actual device of the above nature, type 56 and 76 tubes have been used. The telephone line [-4 is connected to the grid and cathode respectively of the vacuum tube 4 through a resistance of two million ohms in series with each side direct to the grid and cathode, the negative side to the grid and the positive side to the cathode. These values have been found satisfactory for use in connection with automatic telephone systems wherein the line voltage is 48 or 50 volts across the line. On manual lines where the line voltage is 24, the cathode resistor 5 has a value of ten thousand ohms instead of two million. The grid resistor remains at two million.

Having described only a typical form and application of my invention, I do not wish to be limited or restricted to the specific form and application herein set forth, but wish to reserve to myself any modifications or variations that may appear to those skilled in the art or fall within the, scope of the following claims.

I claim:

1. In combination with a telephone subscriber's line a relay comprising a thermionic tube having a cathode and anode and a control electrode, means including a resistance connecting the negative side of said subscriber's line to the control electrode'of said tube, means connecting the positive. side of said subscriber's -line to the cathode of said tube, a source of anode potential for said tube, an electro-magneticrelay having circuit opening and closing devices, means connecting said source of anode potential and the wires of said electro-magnetic relay between the cathode and anode of said tube whereby said electro-magnetic relay is energized at such times as said subscriber's line is in use with a. consequent low voltage thereacross, and a device connected to the circuit opening and closing device on said electro-magnetic relay that is put in operation responsive to the energization of said relay.

2. A device adapted to be connected to a telephone line for recording the conversations passing thereover without in any way impairing the normal operation of said line, comprising a sound recording device, a thermionic tube having at least a cathode, a control electrode and an anode, means for connecting the cathode and control electrodes of said tube to the positively polarized and negatively polarized leads respectively of said line, an electro-magnetic relay and a source of anode potential connected in series between the cathode and the anode of said tube, and means "responsive to the energization of said electro magnetic relay for energizing said recording device and responsive to the deenergization of said electro-magnetic relay for deenergizing said recording device.

3. The method of utilizing a vacuum tube relay to control the energization of a sound recording device connected to a telephone line responsive to the use of that line which comprises applying to the control electrode of said tube a potential of such value as to prevent anode current flow when the line is not in use and changing the potential value of said control electrode to a lower value permitting anode current to flow responsive to the use of said line and energizing said recording device'responsive to the flow of anode current.

4. A device in accordance with claim 3 including a signal for indicating when said line and said recording device are energized and deenergized.

CLARENCE E. REEVES.

cannons 0F connzc'non. Pater 1t no. 2,225,573. January 1h, 19m.

cmmzucz 1-2. REEVES.

It is hereby certified that error appears. in the printed specification of the lbOVB numbexrod putent requiring correction as follov'va Page 2, sec-- ond column, line 51;, claim h, (or the claim raferenco numeral "5" read +-2--; and tht" the said Lettexa Patent should be read with this cox-raction therein that the same may conform to the recnrd oi the cuss in the Patent Office.

Sign! and sealed this 25th day of February, A.. 1), 191.

Henry Van Aradale,

(Seal) Acting Cemmiaaioner of .Patents. 

